Tuning arrangement for cavity resonators



Dec. 22, 1942. A. L. SAMUEL I 2,306,282

TUNING ARRANGEMENT FOR CAVITY RESONATORS Filed June 28, 1941 /N 5 N TOP A. 1.. SAMUEL g A TTORNEV Patented Dec. 22, 1942 TUNING ARRANGEMENT FOR CAVITY RESONATORS Arthur L. Samuel, Summit, N. 3., assignor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application June 28, 1941, Serial No. 400,280

3 Claims.

This invention relates to tuning arrangements for resonating chambers, sometimes called cavity resonators, and is particularly applicable to ultrahigh frequency wave technique.

In accordance with the invention one or more slots are provided in the walls of the resonating chamber, the slot being designed to accommodate a slidable conductive plate that may be inserted into the body of the resonator to any desired distance. The tuning depends upon the degree ofinsertion of the conductive plate. The arrangement is adaptable either for coarse or fine tuning adjustments and also to produce frequency modulation in a resonant cavity. The latter effect may be obtained, for example, by making the-conductive plate in a cam-shaped form which may be rotated in any suitable manner. Alternatively, a tuning plate may be vibrated in its own plane to produce frequency modulation.

' A feature of the invention is the provision of a pair of protective plates of conductive material, one at either side of the slot and mounted parallel to the tuning plate to minimize the escape of electromagnetic radiations through the slot while permitting free motion of the tuning plate. Other features and objects of the invention will become evident from the following description in conjunction with the accompanying drawing 'while the scope of the invention is defined in the appended claims.

In the drawing the single figureshows a resonating chamber associated with an electron beam tube and provided with a plurality of tuning plates.

The envelope of the tubeis indicated at I and encloses an electron beam emitting device or electron gun indicated generally at 2 and mounted upon an inwardly extending stem 3 in conventional manner. The tube also containsa collector electrode 4, a pair of electrodes 5 and 8 defining an input gap I and a pair of electrodes 8 and 9 defining an output gap. The electrodes 5 and 9 are connected with an outer casing l0, while the electrodes 6 and 8 are connected to an inner casing II, the electrodes, connections and casings all being preferably of high conductivity. The resonant chamber is comprised between the casings l and H. A conductive tuning plate l2 projects into the interior of the resonant chamber through a suitable slot in the casing l0 and is guided by suitable flanges It. Means such as a rack and pinion device it adjustable by means of a knob I is connected with the plate I! in any suitable manner. Al-

. engagement in a slot I], which plate may be manually adjusted without the use of any mechanical gearing.

' To eilect frequency modulation a plate l8 may be provided of cam-like form with any desired shape and may be suitably mounted so as to partially extend into the interior of the resonating chamber. The plate may be rotated by a motor ill or other suitable means. Protective plates and 2| of conductive material closely spaced from the plate l8 may be provided, if desired, to minimize the escape of electromagnetic radiations through the slot into which the plate I8 projects and at the same time to permit free rotation of the plate.

A fine adjustment may be obtained by employing a single tuning plate and larger adjustments may be secured by the use of a plurality of plates moved simultaneously or successively in any suitable manner.

What is claimed is:

1. The combination of a cavity resonator, a conductive plate projecting into the interior of the resonator through a slot in the wall thereof, means for varying the extent of projection of the plate within the chamber and a pair of protective plates of conductive material, one at either side of said slot and mounted parallel to said variable plate to minimize the escape of electromagnetic radiations through said slot while permitting free motion of said variable plate. v

2. Means for modulating the frequency of oscillations in a resonating cavity comprising a rotatable conductive cam-shaped pl'ate variably extending into the interior of the resonating chamber through a slot in the wall and a pair of protective plates of conductive material, one at either side of said slot and mounted parallel to said rotatable plate to minimize the escape of electromagnetic radiations through said slot while permitting free motion of said rotatable plate.

3. Means for producing cyclic variations in 

